It is well known that abnormalities of coagulation and fibrinolysis frequently take place during the course of cerebrovascular diseases. In this paper, coagulation and fibrinolytic studies were performed during the course of acute stage through chronic stage of subarachnoid hemorrhage. Tested items were partial thromboplastin time, prothrombin time, FDP, alpha 2-plasmin inhibitor, antithrombin III, fibrinogen, besides, fibrinopeptide A (FPA), and fibrinopeptide B beta (FPB beta) which were being worthy of note. Blood were sampled from peripheral vein (V) and internal jugular vein at jugular bulb (J). And, moreover, cerebrospinal fluid (L) were collected as possible as we could for measuring FPA and FPB beta. The obtained results were summarized as follows; Within forty-eight hours from the onset of subarachnoid hemorrhage, FPA-V, J,L and FPB beta-V, J,L were statistically higher than those of control. FPA-J and FPB beta-V, J, within forty-eight hours from the onset were statistically higher in the cases with brain death than in the survived cases. On the third to fifth day from the onset when so called cerebral vasospasm became apparent to begin, FPA and FPB beta had a tendency to be higher than other periods. Increase of fibrinogen delayed from the peaks of FPA and FPB beta showing the peaks at the seventh to the fourteenth day from the onset of subarachnoid hemorrhage. In three cases with symptomatic vasospasm, FPA and FPB beta showed maximal values two to four days prior to the appearance of symptomatic cerebral vasospasm. Other tests were all within normal limits.(ABSTRACT TRUNCATED AT 250 WORDS)